Sphenoid Face Research Articles

Using the Middle Turbinate to Protect the Skull Base in Endoscopic Transsphenoidal Surgery: A Cadaver Study.

Inadvertent intracranial injury from nasogastric tube (NGT) placement is a described and potentially fatal complication following endoscopic transsphenoidal hypophysectomy (TSH). This cadaver study assessed the role of middle turbinate (MT) preservation and medialization in preventing accidental skull base injury from NGT insertion after TSH. Methods: Standard approach for TSH was performed on 3 human cadavers. MTs were placed into neutral position (MTN), then medialized via suture pexy to the septum (MTP), and subsequently resected (MTR). After each stage, 3 blinded individuals passed a 10 F Dobhoff and a 16 F NGT on each side of each cadaver (5 passes per side). Using endoscopic visualization, each pass was scored by a blinded reviewer based on the first contact point of the tube (0 = nasopharynx, 1 = inferior sphenoid face, 2 = sphenoid sinus), with higher scores suggestive of increased risk of intracranial injury. Results: There were 270 Dobhoff and 270 NGT passes scored. Data was divided into 3 groups based on presence and position of the MT. Significant differences were demonstrated between all three groups [one-way ANOVA: Dobhoff F(2,267) = 6.981, p = 0.001], [NGT F(2,267) = 17.582, p < 0.001]. There were significant differences between means for MTN versus MTP groups [Dobhoff (0.43 vs 0.22, p = 0.007), NGT (0.73 vs 0.28, p < 0.001)] and MTP versus MTR groups [Dobhoff (0.22 vs 0.55, p < 0.001), NGT (0.28 vs 0.81, p < 0.001)], indicating that the presence and position of the MT can significantly affect the accessibility of the sphenoid sinus interior after TSH. There was a trend toward lower means in the MTN group compared to the MTR group. Conclusion: MT preservation and deliberate medialization against the septum may reduce risk of inadvertent intracranial NGT injury in postop TSH patients. This simple maneuver should be considered in all routine TSH procedures.

Morphometric Alterations of the Sphenoid Ostium and other Landmarks in Acromegaly: Anatomical Considerations and Implications in Endoscopic Pituitary Surgery.

The sphenoid ostium (SO) is an important landmark for the endoscopic surgeon. Changes in size and position of the SO and variations in other skull base landmarks in acromegalics have not been adequately evaluated. The authors evaluated the morphometry and location of the SO and other landmarks in acromegaly and compared these findings with those in nonfunctioning pituitary adenomas (NFPAs). In this retrospective case-control study, the dimensions and location of the SO and other skull base landmarks were radiologically evaluated in 18 patients with growth hormone (GH)-secreting adenomas. These findings were analyzed in relation to preoperative GH levels and compared with 18 age- and sex-matched controls with NFPAs. The dimensions of the SO were significantly larger in the GH-adenoma group (P < 0.05). The SO was further from the midline (P = 0.04) and closer to the sphenopalatine foramen (SPF) (P = 0.02) in the GH-adenoma group, and this finding correlated with increasing preoperative GH levels. Acromegalics demonstrated larger intracavernous carotid diameters (P = 0.05) and smaller intercarotid distances than the patients with NFPAs (P = 0.02). The SO is larger and located higher up in the sphenoid face and closer to the SPF in patients with GH adenomas. Increasing GH levels in these patients correlate with the upward and lateral displacement of the SO. These patients demonstrate larger intracavernous carotid diameters and smaller intercarotid distances than patients with NFPAs. These morphological alterations are of particular relevance to the pituitary surgeon.

Postoperative epistaxis and sphenoid sinus ostial stenosis after posterior septal branch injury during sphenoidotomy.

Postoperative arterial epistaxis and sphenoid sinus stenosis after sphenoidotomies for endoscopic sinus surgery (ESS) and transsphenoidal approaches (TSAs) are uncommon. One potential source of epistaxis after sphenoidotomy is the sphenopalatine artery's posterior septal branch (PSB). PSB injury, in addition to other factors, could increase the risk of sphenoid stenosis. The purpose of this study was to determine incidence of, and risks factors for, the following outcomes after sphenoidotomy: PSB injury; postoperative epistaxis from the injured PSB; and sphenoid stenosis after PSB injury. A single-institution, prospective case series was conducted based on 233 sphenoidotomies performed during ESS (n = 163) and TSAs (n = 70). Outcome measures included intraoperative PSB injury, postoperative epistaxis from the PSB, and sphenoid stenosis. The incidence of PSB injury was 17.2% during ESS-related sphenoidotomies, and 5.7% during TSA-related sphenoidotomies (p = 0.010). After PSB injury during ESS- and TSA-related sphenoidotomies (n = 32), there was 1 instance of epistaxis from the PSB (3.1%). Of the 161 ESS-related sphenoidotomies, 6 developed complete or near-complete stenosis (3.7%), which was more likely to occur with smaller anterior sphenoid face dimensions (p = 0.001). PSB injury, revision sphenoidotomy, and other factors did not increase the risk of stenosis. None of the TSA-related sphenoidotomies stenosed completely. Median follow-up was 7 months. PSB injury occurred in 17.2% of ESS-related sphenoidotomies and 5.8% of TSA-related sphenoidotomies. After PSB injury, postoperative epistaxis from the PSB was rare (3.1%). After ESS-related sphenoidotomies, sphenoid stenosis was rare (3.7%), and was more likely to occur with smaller sphenoid dimensions, but not with PSB injury or other factors.

Quantitative Analysis of Surgical Working Space During Endoscopic Skull Base Surgery

Objectives Selective dissection of intranasal anatomy may improve visualization and maneuverability at the skull base. We aimed to quantify the dimensions of working space and angles achieved following sequential removal of intranasal structures using an endoscopic transphenoidal approach to the skull base. Methods Cone beam computed tomography scans of four cadaveric heads were obtained for registration of an optical tracking system. Each head was sequentially dissected: (1) sphenoidotomy and limited posterior septectomy, (2) unilateral partial middle turbinectomy, (3) bilateral partial middle turbinectomy, and (4) wide posterior septectomy. The maximal craniocaudal and mediolateral distance (mm) and angle (degrees) reached were calculated at the sphenoid face and sella. Data were analyzed using descriptive statistics and tests of statistical significance. The significance level was set at p ≤ 0.05. Results A significant improvement in both dimensions of working space was observed with each stage of dissection at the level of the sphenoid face. Maximal working space was achieved following bilateral middle turbinectomy and wide posterior septectomy with a 38 and 29% increase in working space in the mediolateral and craniocaudal dimensions, respectively. The largest stepwise increase in working space was observed with unilateral middle turbinectomy (mediolateral: 24 ± 3 mm and craniocaudal: 20 ± 3 mm). A trend toward improved degrees of visualization was observed with each stage of dissection but was not statistically significant. Conclusion Approaches to the skull base can be enhanced by selective unilateral/bilateral partial middle turbinectomy and posterior septectomy being performed to improve visualization and maximize surgical working freedom.

The relationship of the natural sphenoid ostium to the skull base.

Various intranasal landmarks have been described to aid in the localization of the natural sphenoid sinus ostium. The objectives of this study are to identify the ostium location relative to the skull base and assess the relationships between the location of the ostium and sphenoid disease or pneumatization pattern. Descriptive study. Consecutive Xoran Mini-CAT (Ann Arbor, MI) scans of patients with no history of sinus surgery (n = 202) were evaluated. The natural sphenoid ostium was identified in axial, coronal, and sagittal planes. Distances from the planum to the ostium and from the planum to the sinus floor were calculated. Lund-Mackay score and pneumatization pattern were recorded for each sphenoid sinus. The mean distance from planum to ostium was 11.2 ± 2.6 mm (range 4.4-19.2). On average, this encompassed 45.5% ± 10% of the total sphenoid height. ANOVA with posthoc Tukey analysis revealed that the ostium was closer to the planum in sinuses with sellar (P = 0.05) or presellar (P = 0.02) pneumatization, compared to those with postsellar pneumatization. There was no significant relationship between the ostium location and degree of sinus disease. There was a significant difference in the pneumatization pattern between males and females (P = .04). More males had postsellar pneumatization than expected, and more females had sellar pneumatization than expected. The natural ostium of the sphenoid sinus is located at approximately the midpoint of the sphenoid face. Nevertheless, significant variability can be observed based on the pneumatization pattern. Surgeons should recognize that the ostium may be closer to the skull base when the sinus is less pneumatized.

Compartmental endoscopic surgical anatomy of the medial intraconal orbital space

Surgical management of intraconal pathology represents the next frontier in endoscopic endonasal surgery. Despite this, the medial intraconal space remains a relatively unexplored region, secondary to its variable and technically demanding anatomy. The purpose of this study is to define the neurovascular structures in this region and introduce a compartmentalized approach to enhance surgical planning. This study was an institutional review board (IRB)-exempt endoscopic anatomic study in 10 cadaveric orbits. After dissection of the medial intraconal space, the pattern and trajectory of the oculomotor nerve and ophthalmic arterial arborizations were analyzed. The position of all vessels as well as the length of the oculomotor trunk and branches relative to the sphenoid face were calculated. A mean of 1.5 arterial branches were identified (n = 15; range, 1-4) at a mean of 8.8 mm from the sphenoid face (range, 4-15 mm). The majority of the arteries (n = 7) inserted adjacent to the midline of medial rectus. The oculomotor nerve inserted at the level of the sphenoid face and arborized with a large proximal trunk 5.5 ± 1.1 mm in length and multiple branches extending 13.2 ± 2.7 mm from the sphenoid face. The most anterior nerve and vascular pedicle were identified at 17.0 and 15.0 mm from the sphenoid face, respectively. The neurovascular supply to the medial rectus muscle describes a varied but predictable pattern. This data allows the compartmentalization of the medial intraconal space into 3 zones relative to the neurovascular supply. These zones inform the complexity of the dissection and provide a guideline for safe medial rectus retraction relative to the fixed landmark of the sphenoid face.

How we do it: mini posterior septal artery flap for coverage after transphenoidal approaches

We propose a novel posterior nasal flap for use in endoscopic approaches to the sella and parasellar region that involve resection of the sphenoid face and a posterior nasal septectomy. It involves elevation of the mucosa of the posterior septum and sphenoid face with preservation of the angiosome based on the posterior septal artery. This flap has the advantages of maximal mucosal preservation in order to optimize postoperative healing and has been demonstrated to permit future elevation of a complete naso-septal flap for reconstruction of anterior skull base defects. An illustration of the technique is provided.

Validation of a grading system for the attachment of the superior turbinate to the sphenoid face

The attachment of the superior turbinate to the sphenoid face may be an important factor in determining the approach for sphenoidotomy. We sought to validate a previously described 4-type grading system for superior turbinate attachment (Type: A, within its medial one-third; B, in its middle one-third; C, to its lateral one-third; and D, directly to the orbit) to the face of the sphenoid sinus and to make recommendations for its use in determining the method of sphenoidotomy (transethmoidal vs transsphenoethmoidal). Single-slice images through both sphenoid sinus ostia were obtained from axial series of computed tomography (CT) scans. Eighteen (36 ostia) sets of scans were used. Attachment type (A-D) in each image was classified by 10 experienced sinus surgeons and compared against a "gold standard" grading performed by the senior author (A.J.), who was the developer of the grading system. Mean accuracy was 63% (95% confidence interval [CI], 54%-72%) for the 4-type grading system. When Types A+B and Types C+D were grouped together, mean accuracy was 91% (95% CI, 84%-97%). For the 2-group classification system, bootstrap analysis suggested that 97% of physicians attain an accuracy of at least 80%. Accuracy using the 4-type classification is too low to be practically useful. Accuracy using the 2-group system may be sufficiently high to be a useful aid in selecting a surgical approach. We recommend a transethmoid sphenoidotomy for Types A and B and a transsphenoethmoidal approach to the sphenoid for Types C and D.

The bipedicled anterior septal flap

Pedicled mucosal flaps are the preferred method of endoscopic skull base reconstruction. Vascularized coverage of the anterior and posterior frontal tables remains a challenge given the lack of large caliber vessels supplying the anterior septum. The objective of this study was to define a novel bipedicled anterior septal (BAS) flap that is hypothesized to be capable of providing reproducible coverage of these difficult areas. Radioanatomic and cadaveric study. The flap outline was superimposed over nine midline sagittal computed tomography images. The pedicles are comprised of the septal branch of the superior labial artery and the nasopalatine artery. The flap length subtended the distance from the incisive canal to the sphenoid face at the level of the choanal arch. Radiometric analysis of the flap length to base ratio and anterior/posterior frontal table coverage were calculated. These projected values were confirmed in four cadaveric dissection specimens. The mean flap length was 39.64 ± 4.26 mm with a mean length:base ratio of 3.29 ± 0.70 and a total surface area of 916.46 ± 262.66 mm(2) . The flap was estimated to provide coverage of 100.31 ± 21.34% of the frontal beak and 50.74 ± 32.54% of the posterior frontal table. In all cadaveric specimens the flap extended beyond the superior aspect of the frontal beak and at least 50% of the posterior table. The BAS flap represents a novel septal mucosal flap based on two well-defined arterial inputs. This flap is capable of providing reliable vascularized coverage of the posterior frontal table and the frontal beak following frontal drillout.

Nasoseptal “Rescue” flap: A novel modification of the nasoseptal flap technique for pituitary surgery

The introduction of the pedicled nasoseptal flap (NSF) has decreased postoperative cerebrospinal fluid (CSF) leak rates from >20% to <5% during expanded endoscopic skull base surgery. The NSF must be raised at the beginning of the operation to protect the posterior pedicle during the expanded sphenoidotomy. However, in most pituitary tumor cases, an intraoperative CSF leak is not expected but at times encountered. In these cases, a "rescue" flap approach can be used, which consists of partially harvesting the most superior and posterior aspect of the flap to protect its pedicle and provide access to the sphenoid face during the approach. The rescue flap can be fully harvested at the end of the case if the resultant defect is larger than expected, or if an unexpected CSF leak develops. This technique minimized septum donor site morbidity for those patients without intraoperative CSF leaks. The rescue flap technique allows for binaural and bimanual access to the sella without compromise of the pedicle during the extended sphenoidotomies and tumor removal. If an intraoperative CSF leak is encountered, the rescue flap is then converted into a normal nasoseptal flap for skull base reconstruction. If no leak is obtained, then the patient does not suffer additional donor site morbidity from the full flap harvest. This new technique allows for sellar tumor removal prior to the nasoseptal harvest, thereby eliminating donor site morbidity for those pituitary tumor patients who do not have an intraoperative CSF leak.

Radiographic and Anatomic Characterization of the Nasal Septal Swell Body

To analyze the radiographic, anatomic, and histologic characteristics of the nasal septal swell body. Computer-aided analysis of magnetic resonance images (MRIs) and histologic examination of cadaveric nasal septa. Tertiary medical center. Fifty-four head MRI studies were performed on adult live patients; we also used 10 cadaveric nasal septa. Radiographic dimensions of the swell body and distances to other nasal landmarks were measured. Nasal septa and swell body histologic characteristics were evaluated using light microscopy. Relative proportions of vascular, connective, and glandular tissues within the swell body and the adjacent septum were compared. The swell body was fusiform shaped and located anterior to the middle turbinate, with mean (SD) width of 12.4 (1.9) mm; height, 19.6 (3.2) mm; and length, 28.4 (3.5) mm. The epicenter was 24.8 (2.9) mm from the nasal floor, 43.9 (4.1) mm from the nasal tip, and 39.0 (4.6) mm from the sphenoid face. Histologic analyses revealed that, compared with adjacent septal mucosa, the swell body contained significantly more venous sinusoids (37% vs 16%, P<.001) and fewer glandular elements (28% vs 41%, P<.001). The swell body is a conserved region of the septum located anterior to the middle turbinate approximately 2.5 cm above the nasal floor. The high proportion of venous sinusoids within the swell body suggests the capacity to alter nasal airflow. Additional study is required before these findings are used in a clinical setting.

Safety of Ethmoid Sinus Drug-Eluting Catheter Insertion

We sought to evaluate an instrument that allows a drug-eluting catheter to be inserted into the ethmoid sinuses and to demonstrate its safety and reproducibility in a cadaver model. A drug-eluting catheter was placed into 12 cadaveric anterior and posterior ethmoid sinuses by use of a trocar-based insertion device. The device's position was analyzed with computed tomographic scans, and postprocedural dissection was performed. The drug-eluting catheter system was successfully inserted in all ethmoid sinuses without injury to the medial orbital wall, skull base, or sphenoid face. The final position of the distal tip of the catheter averaged 8.1 mm (root mean square [RMS], 3.3 mm) from the skull base, 5.6 mm (RMS, 3.5 mm) from the sphenoid face, and 5.0 mm (RMS, 3.5 mm) from the lamina papyracea; the proximal tip was at the face of the ethmoid bulla and 17.1 mm (RMS, 3.5 mm) below the skull base. A trocar-based instrument can relatively safely and reproducibly introduce a drug-eluting catheter into the ethmoid sinuses without injuring the skull base, lamina papyracea, or sphenoid face. This device may allow safe topical drug delivery into the ethmoid sinuses and serve as a vehicle to treat chronic ethmoid sinusitis with direct and sustained topical therapy.

A Comparison of two Sphenoidotomy Approaches using a Novel Computerized Tomography grading System

Endoscopic management of sphenoid sinus disease has great potential for surgical complications. A variety of endoscopic surgical techniques have been described for entering the sphenoid sinus. The utility of these surgical techniques is based on the position of the superior turbinate attachment to the sphenoid face (Parson's ridge). We introduce a novel computerized tomography (CT) grading system for the attachment of the superior turbinate to the sphenoid face. Using this new grading system, we recommend a safer systematic approach for entry into the sphenoid sinus. A grading based on the attachment of the superior turbinate to the sphenoid face at the level of the natural sphenoid ostium was developed. A total of 53 patients were enrolled. Types A, B, and C refer to the superior turbinate attachment at the medial, middle, or lateral third of the anterior sphenoid face, respectively, and type D refers to orbital attachment of the superior turbinate. The surgical approach used (superior turbinate intact [STI] or superior turbinate resection [STR]) was recorded and correlated to the type of superior turbinate attachment. The overall incidence of the various superior turbinate attachments were 40% (41) for type A, 41% (42) for type B, 18% (19) for type C, and 1% (1) for type D. STR was used in 38 sides (44%) and STI was used in 48 sides (56%). Spearman correlation study showed that the closer the superior turbinate attachment was to the orbit the more likely STR was used as the choice of entry into the sphenoid (p < 0.001). To perform a safe sphenoid entry it is pertinent to evaluate the superior turbinate attachment to the sphenoid face before making a decision on the method of entry.

Safety of Ethmoid Sinus Drug-Eluting Catheter Insertion

Problem The objective is to develop an instrument which allows a drug-eluting catheter to be safely and reproducibly inserted into the ethmoid sinuses. Methods A trochar-based insertion device was designed to allow delivery of a drug-eluting catheter into the anterior and posterior ethmoid sinuses. It was inserted into 12 cadaveric ethmoid sinuses under endoscopic and fluoroscopic guidance. CT scans were performed pre-, intra-, and post-procedure. The device's position was analyzed and the proximity to the skull base, lamina papyracea, and ethmoid face was measured. The specimens were then dissected and evaluated for skull base, sphenoid face, or lamina papyracea injury. Results The drug eluting catheter system was successfully inserted into the ethmoid sinuses of all 12 cadaver sides without injury to either the medial orbital wall or the skull base as confirmed by post-procedure CT scan and dissection. The final position of the distal tip of the stent averaged 8.1mm (RMS = 3.3) from the skull base, 5.6mm (RMS=3.5) from the sphenoid face, and 5.0mm (RMS=3.5) from the lamina papyracea; the proximal tip was at the face of the ethmoid bulla and 17.1mm (RMS=3.5) below the skull base. Conclusion This study demonstrates that a trochar-based instrument can safely and reproducibly introduce a drug-eluting catheter into the ethmoid sinuses without skull base or lamina papyracea injury. This device may allow safe topical drug delivery into the ethmoid sinuses and provide chronic ethmoid sinusitis patients an alternative to ethmoidectomy. Significance The primary surgical therapy for chronic ethmoid sinusitis is ethmoidectomy; topical therapy has been widely used in the management of chronic ethmoid sinusitis only after ethmoidectomy. This study shows a drug-eluting catheter can be safely and reliably inserted into virgin ethmoid sinuses in order to allow the topical elution of medications into the ethmoids without ethmoidectomy. Support Acclarent supplied cadaveric specimens.

Contour and Paired‐Point Registration in a Model for Image‐Guided Surgery

This study assesses target registration error (TRE) of contour-based registration (CBR) and paired-point registration (PPR) for endoscopic sinus surgery. The experimental registration model consisted of a replica of a human head (Sawbones #1345-27; Pacific Research Laboratories, Vashon, WA). Twelve surface fiducial markers were affixed to the simulated skin on the model, and titanium screws were placed in the regions of the anterior ethmoid (AE) and sphenoid face (SF). An axial computed tomography scan (1-mm slice thickness) was then obtained. Registration was then performed on the InstaTrak 3500 Plus (GE Surgical Navigation & Visualization, Lawrence, MA) with the standard PPR protocol with 12 points and CBR protocol with 500, 250, 125, 50, and 4 points. TRE was then calculated at the AE and SF targets. Target registration error was significantly lower for paired-point registration compared with contour-based registration (AE, 0.5 mm vs. 1.5 mm, P < .0001; SF, 0.8 mm vs. 1.5 mm, P < .0001). Among contour-based registration protocols, target registration error at the sphenoid face was lowest with 50 points (1.5 mm, P < .02). At the anterior ethmoid, contour-based registration with 50 points produced a lower target registration error than contour-based registration with 125 points (1.5 vs. 1.8 mm, P < .01). Other target registration error values for CBR were similar at both regions. The target registration error interquartile range was lowest with CBR-125 at both regions. Paired-point registration provided significantly lower target registration error. Contour-based registration with 125 points (and possibly as few as 50 points) produces clinically acceptable target registration error. This registration model elucidates important concepts about registration for surgical navigation for sinus surgery.

A review of the endoscopic approach to the pituitary through the sphenoid sinus

The refinement of minimally invasive endoscopic techniques has resulted in 'pure' endoscopic endonasal trans-sphenoidal surgery, which is a new approach for the removal of pituitary tumors. This procedure is performed via a wide anterior sphenoidotomy with detachment of the septum from the sphenoid face, and avoids the use of a trans-sphenoidal retractor and any intraoral or nasal incisions. Straight and angled endoscopes are used throughout the procedure to provide a wide view of the sella and are manipulated by a co-surgeon. This technique represents an improvement over pituitary microsurgery, with decreased post-operative morbidities and a shortened postoperative stay, and it eliminates the need for packing while providing an opportunity to monitor the sella after surgery. The technique has been established as being efficacious and safe. It incorporates image-guided surgery, with the fusion of computer tomography and magnetic resonance imaging, and employs new and dedicated instrumentation. Training in endoscopic techniques is required. Future advancements in intraoperative imaging, cranial base reconstruction, and robotics will make this technique even more successful.

Sagittal and Coronal Dimensions of the Ethmoid Roof: A Radioanatomic Study

Understanding the anatomy of the ethmoid roof is critical to safe surgical outcomes. Normative data regarding the height and slope of this region have been somewhat limited, derived primarily from cadaveric coronal computed tomography (CT) studies. With triplanar imaging programs, precise multidimensional measurements of the ethmoid roof are now possible. We present a radioanatomic study to characterize normative sagittal and coronal dimensions of the ethmoid roof. Bilateral measurements were taken in 100 consecutive sinus CT scans using ThinClient 3D software. In the sagittal plane, the height of the ethmoid roof was measured in quadrants at five equidistant points between the frontal beak and sphenoid face, referencing the nasal floor. In the coronal plane, the ethmoid roof was measured at three points at the level of the anterior ethmoid artery and at two points at the junction of the posterior ethmoid and sphenoid sinuses. When examined sagittally, the right side showed significantly lower skull base heights in the anterior ethmoid compared with the left side (59.0 mm versus 59.8 mm, p = 0.017; 53.7 mm versus 54.5 mm, p = 0.0004). Coronal measurements of the anterior ethmoid roof showed similar significant differences. The anterior ethmoid roof had greater asymmetries of height compared with the posterior ethmoid roof, which was fairly constant. This study provides numerical correlates to accepted concepts regarding the shape and slope of the ethmoid roof. Differences in height of the skull base between right and left sides, especially in the anterior ethmoid sinus, may be an important surgical consideration. The posterior ethmoid roof appears to be relatively constant and should serve as a reliable surgical landmark.

Use of the superior meatus and superior turbinate in the endoscopic approach to the sphenoid sinus

Endoscopic surgery of the posterior ethmoid and sphenoid sinuses can present the operator with a considerable challenge. Although endoscopic training and physician experience have increased significantly in the past decade, surgical complications such as optic nerve trauma and cerebrospinal fluid leak still occur. Surgeons reporting such complications cite a lack of orientation within the dissection field as a primary cause. Because endoscopic sinus surgery is now being performed more routinely, surgical strategies designed to reduce the risk of complications are more important than ever. An anatomic landmark that could reliably orient the dissection within the posterior ethmoids and guide the surgeon to the sphenoid sinus could reduce the possibility of such adverse outcomes. In our experience identification of the superior meatus and superior turbinate provides a reliable landmark within the dissection field that can ensure surgical orientation to the operator. This technique allows safe, reliable dissection of the posterior ethmoids and an efficient approach to the sphenoid sinus, especially in patients undergoing revision surgery. In this article our technique for the identification and definition of the superior meatus and superior turbinate is presented, and the advantages of using this landmark in sinus surgery are discussed. In our experience identification of the superior meatus, superior turbinate, posterior skull base, and medial orbital wall defines a parallelogram-shaped box, which delineates the sphenoid face. This box provides the necessary orientation to guide the surgeon’s entrance into the sphenoid sinus through the posterior ethmoid sinus (as Messerklinger described). Techniques for identifying the superior turbinate and meatus and for entering the sphenoid are detailed. (Otolaryngol Head Neck Surg 1999;120:308-13.)

Endoscopic transseptal transsphenoidal hypophysectomy with three-dimensional intraoperative localization technology.

Endoscopic transseptal transsphenoidal hypophysectomy with three-dimensional intraoperative localization technology.

Sinus lateralis in endoscopic ethmoidectomy.

To characterize the anatomy of the sinus lateralis and enable a more accurate and safe approach to endoscopic ethmoidectomy. An anatomic study of 33 cadaver heads providing a prospective evaluation of 50 ethmoid sinuses. The sinus lateralis, in particular, was thoroughly examined and typical variations were classified into four categories. A technique using the sinus lateralis as a critical landmark is described which allows calculated removal of anterior ethmoid cells in a posterior-to-anterior direction, avoiding inadvertent entry into the posterior ethmoid. Prospective evaluation of this technique in 12 pediatric patients found it to be safe and particularly useful for neophyte endoscopic surgeons. Endoscopic examination of 50 cadaver sinuses using 0-, 30-, and 70-degree, 4-mm telescopes to dissect the anterior ethmoid. The characteristics of each sinus lateralis were documented. To confirm the endoscopic findings, we grossly examined each specimen. Four different categories of sinus lateralis formation were identified: type I (n = 22), posterosuperior extension to skull base; type II (n = 15), posterior extension to sphenoid face; type III (n = 8), abrupt termination posterior to ethmoid bulla; and type IV (n = 5), extension into posterior ethmoid through dehiscent basal lamella. The sinus lateralis is a consistent feature of the anterior ethmoid. Type I and II patterns are most conducive to the aforementioned technique. Type III is the most difficult to identify endoscopically, whereas type IV is most apt to encourage an unplanned posterior ethmoidectomy. Regardless of the chosen ethmoidectomy technique, careful assessment of the sinus lateralis should enable more accurate and safe removal of ethmoid disease with reduced complications.